Various types of excavation machinery initiate an excavation operation at an above-ground position 37 and employ a powered excavation tool to penetrate the earth to a specified depth d. Certain excavation machines are designed to initially excavate earth in a generally vertical direction with respect to the ground surface, and then proceed with excavation in a generally horizontal direction. For these and other excavation machines, the time required to complete the initial vertical excavation effort is typically appreciable.
One such excavation machine that performs an initial vertical excavation prior to a horizontal excavation is termed a track trencher. A track trencher 30 excavation machine, shown in FIGS. 1 and 2, typically includes an engine 36 coupled to a left track drive 32 and a right track drive 34 which together comprise a tractor portion 45 of the track trencher 30. An attachment 46, usually mounted on a boom 47, is typically coupled to the rear of the tractor portion 45 and typically performs a specific type of excavating operation.
A ditcher chain 50 is often employed to dig relatively large trenches at an appreciable rate. The ditcher chain 50 generally remains above the ground in a transport configuration 56 when maneuvering the trencher 30 around a work site. During excavation, the ditcher chain 50 is lowered to a below-ground position 39, penetrating the ground and excavating a trench at the desired depth and speed while in a trenching configuration 58.
Another popular trenching attachment is termed a rock wheel 60 in the art, shown in FIG. 3, and may be operated in a manner similar to that of the ditcher chain 50. Additional attachments, such as a TERRAIN LEVELER™, manufactured by Vermeer Manufacturing Company of Pella, Iowa, are also known in the art and are also operated in a similar manner.
A track trencher excavation machine typically employs one or more sensors that monitor various physical parameters of the machine. The information gathered from the sensors is generally used as an input to regulate a particular machine function, and/or to provide an operator with information, typically by transducing a sensor signal for communication to one or more screens 500 or display instruments, such as a tachometer, for example.
As shown in FIG. 4, a manual boom position (up/down) switch 583 is typically provided to allow the operator to control the movement and vertical position of the attachment 46. An auto-plunge switch 585 is typically provided to allow the operator to control the movement and position of the attachment boom 47 in conjunction with engine 36 speed feedback regulation. The feedback regulation typically monitors an engine 36 speed and reduces an attachment boom 47 movement speed during heavy engine loading and increases the attachment boom 47 movement speed during light engine loading. An attachment drive speed control 598 is typically provided to allow the operator to select and adjust the speed of the attachment 46 drive. An engine throttle 506 is typically provided to limit the engine 36 speed. These controls allow the operator to raise and lower the attachment 46 between the above-ground position 37 and the below-ground position 39 and perform an excavation operation termed a plunge-cut.
It is generally desirable to maintain the engine 36 at a constant output level during excavation which, in turn, allows the trenching attachment 46 to operate at a constant trenching output level. In certain applications, it is desired to maintain the engine 36 at its maximum power output level. Controlling the trencher 30 during plunge-cut excavation by employing a feedback control system as disclosed in U.S. Pat. No. 5,768,811, issued Jun. 23, 1998, eliminates the need for the operator to make frequent adjustments to the manual boom position switch 583 in order to maintain the engine 36 at a target engine output level.
There is a desire among the manufacturers of excavation machinery to minimize the difficulty of operating such machines and to increase their productivity while excavating and, more particularly, while plunge-cutting. It is also desired that high levels of productivity are achieved while excavating and plunge-cutting under a variety of operating conditions and environments and that the excavation machinery be tunable and adaptable to these varying conditions. Furthermore, there is another desire among the operators of such excavation machinery to specify the desired depth d to which the excavation machinery excavates and have that depth d automatically maintained without further operator intervention. The present invention fulfills these and other needs.